From then on, Arsenal looked like a huge weight had been lifted from their collective shoulders and played with much more freedom.

Understandably, Albion were furious.

“It was a decision that changed the game,” said ­manager Steve Clarke.

“There was zero contact by Steven Reid. It wasn’t even close on the penalty.”

To be fair, Arsenal should have had the game wrapped up by the time of a second contentious issue in the 64th minute.

Albion substitute Goran Popov appeared to be fouled by Alex Oxlade-Chamberlain, but the winger was allowed to continue his run and was chopped down by Chris Brunt in the area.

“I have no problem with the penalty,” said Clarke.

“But the referee had been giving soft free-kicks all ­afternoon didn’t see that foul. We have some fantastic ­referees in this country, but today we had one of the ­poorest of a good group.”

In spite of their frustration, the Baggies would have to admit that at the heart of ­Arsene Wenger’s victory was an immense performance from Jack Wilshere.

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Wilshere is now approaching full fitness after a year of injury and frustration – and this was Wilshere at his best. He was creative, imaginative and, when the occasion ­demanded, showed a spikey edge to his game.

Along with Cazorla, he ­dominated the central area.

However, Albion – after their hugely impressive start to the season – have hit something of a wall.

Decisions that had gone their way are now going against them.

And they did have valid complaints about the two ­penalities that secured ­Arsenal their much-needed win after recent weeks when the judgment of Wenger and the club’s financial policy have been brought into ­question by disaffected fans.

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The enigmatic Gervinho – who can go from the brilliant to the bizarre in a heartbeat – missed a chance and so did Cazorla as Arsenal set the tempo that was so badly ­lacking against Swansea seven days earlier.

As Arsenal breathed a sigh of relief, the chances came.

“The one negative for us was that we didn’t take them,” said Wenger.

Lukas Podolski was the worst culprit after Wilshere set him up six yards from goal. The Germany international did the hard bit – but somehow screwed the ball over the bar which looked impossible from his position.

“We are now beginning to see the best of Jack Wilshere,” said Wenger.

“You have to be patient and we have been. Today we saw zip in his play. But I am proud of the spirit my team showed. Our spirit has been questioned because of a flat performance last week. But we were ready for a fight. That is the sign of good players - when you have to win, you win.”